Supposedly, epub format books purchased elsewhere and converted to mobi for the Kindle 3 can end up getting Amazon's print-edition page number info.

Anyone seen this or know if it's true?

If true, how does it happen?
I would have thought that the page number info was tied to a specific filename or ASIN, but if converted books get the info, then it must be based on title/author metadata or similar? Surely the Kindle isn't phoning home ebook CONTENT to Amazon?

Yes, but what I mean is, say I get "The Time Machine" by H.G. Wells from epubbooks.com or what have you.
I convert the epub to mobi and put it on my Kindle. Eventually, I see page number info, so I apparently got an .apnx file from Amazon? Did the Kindle phone home with the title and author of every file on my Kindle, and Amazon was nice enough to respond with an .apnx file for any matches in it's database?
I mean, that's really generous of them, in a scary, Big Brother kind of way.
If that is indeed what is happening.
ApK

I convert the epub to mobi and put it on my Kindle. Eventually, I see page number info, so I apparently got an .apnx file from Amazon? Did the Kindle phone home with the title and author of every file on my Kindle, and Amazon was nice enough to respond with an .apnx file for any matches in it's database?

No. If you used Calibre to convert to mobi, then Calibre put the .apnx file on your Kindle. Not Amazon. The Kindle Interface Driver plugin in Calibre now sends the .apnx file file by default.

But they're "calculated" page numbers. They don't coincide with a specific physical incarnation of the book.

Ah. Thanks. That's a much more comfortable explanation.
I rarely use the "send to device" button myself, so I had never noticed this. (I send most stuff via email.)
I had no idea it was an automatic default behavior.

Doing a search, I do indeed see that a few of my own converted ePubs have .apnx files. Neat.

Do you happen to know if there is some signature I can look for in the .apnx to indicate it was created by Calibre? Glancing at the files just with notepad, I presume the ones with a value in the human-readable "ASIN" field came from Amazon, but is there any thing else?